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United States Patent |
5,128,231
|
Itoh
,   et al.
|
July 7, 1992
|
Negative photoresist composition comprising a photosensitizer of a
polyhalogen compound
Abstract
A photoresist composition is disclosed. The photoresist composition
comprises a base resin, a photosensitizer, and a solvent. The base resin
comprises polyhydroxystyrene represented by the following structural
formula (I):
##STR1##
(wherein k is a positive integer). The photosensitizer comprises a
polyhalogen compound(s). The photoresist composition of the present
invention has dry etching resistance characteristics comparable to those
of conventional positive novolak photoresist compositions and can form a
resist pattern with a high resolution and vertical sidewall profiles. This
makes microprocessing possible.
Inventors:
|
Itoh; Toshio (Tokyo, JP);
Sakata; Miwa (Tokyo, JP);
Yamashita; Yoshio (Tokyo, JP);
Asano; Takateru (Tokyo, JP);
Kosuga; Yuuzi (Tokyo, JP);
Umehara; Hiroshi (Tokyo, JP)
|
Assignee:
|
Oki Electric Industry Co., Ltd. (Tokyo, JP);
Fuji Chemicals Industrial Co., Ltd. (Tokyo, JP)
|
Appl. No.:
|
798975 |
Filed:
|
November 29, 1991 |
Foreign Application Priority Data
| Dec 23, 1988[JP] | 63-325386 |
| Nov 30, 1989[JP] | 1-311716 |
Current U.S. Class: |
430/270.1; 430/905; 430/919; 430/923; 430/925; 430/945; 522/2; 522/45; 522/53; 522/59; 522/63; 522/65; 522/67; 522/150 |
Intern'l Class: |
G03F 007/038 |
Field of Search: |
430/925,919,923,905,270
522/67,45,59,63,53,150,65
|
References Cited
U.S. Patent Documents
3779778 | Dec., 1973 | Smith et al. | 430/270.
|
3793033 | Feb., 1974 | Mukherjee | 96/115.
|
4789619 | Dec., 1988 | Ruckert et al. | 430/270.
|
4840867 | Jun., 1989 | Elsaesser et al. | 430/270.
|
4840869 | Jun., 1989 | Kita et al. | 430/270.
|
5034304 | Jul., 1991 | Feely | 430/270.
|
Foreign Patent Documents |
0040535 | May., 1981 | EP.
| |
0232972 | Jan., 1987 | EP.
| |
0319325 | Jun., 1989 | EP.
| |
Other References
A. Bruns et al., Microelectronic Engineering 6(1987) 467-471.
|
Primary Examiner: Hamilton; Cynthia
Attorney, Agent or Firm: Wenderoth, Lind & Ponack
Parent Case Text
This application is a continuation of now abandoned application Ser. No.
07/452,275 filed on Dec. 18, 1989.
Claims
What is claimed is:
1. A negative photoresist composition consisting essentially of:
a base resin,
a photosensitizer, and
a solvent;
said base resin comprising a polyhydroxystyrene represented by the
following structural formula (I):
##STR16##
wherein k is a positive integer; and said photosensitizer comprising a
polyhalogen compound(s).
2. A negative photoresist composition as claimed in claim 1, wherein said
base resin has a weight-average molecular weight of 1,000 to 100,000.
3. A negative photoresist composition as claimed in claim 1, wherein said
photosensitizer is sensitive to at least one member selected from the
group consisting of deep ultraviolet radiation, X-rays, and electron
beams.
4. A negative photoresist composition as claimed in claim 1, wherein said
photosensitizer comprises at least one polyhalogen compound selected from
the group consisting of dichloroalkanes and trichloroalkanes represented
by the following general formula (II):
R.sup.1 --CH.sub.3-l Cl.sub.l (II)
wherein R.sup.1 stands for an alkyl group; and l is 2 or 3, and
polybromoalkanes and polyiodoalkanes represented by the following general
formula (III):
C.sub.m H.sub.2m+2-n X.sup.1.sub.n (III)
wherein X.sup.1 stands for bromine or iodine; and m and n are integers,
provided that they satisfy the formula: 1.ltoreq.n.ltoreq.2m+2.
5. A negative photoresist composition as claimed in claim 1, wherein said
photosensitizer comprises at least one polyhalogen compound selected from
the group consisting of .alpha.-haloester compounds,
.alpha.-halocarboxylic acid compounds, .alpha.-haloketone compounds,
.alpha.-haloaldehyde compounds, .alpha.-haloamide compounds,
N-alkylhaloamide compounds, and N,N-dialkylhaloamide compounds all
represented by the following general formula (IV):
##STR17##
wherein X.sup.2 stands for chlorine, bromine, or iodine; p is an integer
of 1 to 3; and Y stands for an alkoxyl group (--OR.sup.1) in the case of
said .alpha.-haloester compounds, for a hydroxyl group (--OH) in the case
of said .alpha.-halocarboxylic acids, for an alkyl or aryl group
(--R.sup.2) in the case of the .alpha.-haloketone compounds, for hydrogen
in the case of said .alpha.-haloaldehyde compounds, for an amino group
(--NH.sub.2) in the case of said .alpha.-haloamide compounds, for a
primary amine residue (--NHR.sup.1) in the case of said N-alkylhaloamide
compounds, or for a secondary amine residue (--N.sub.2 R.sup.1) in the
case of N,N-dialkylhaloamide compounds.
6. A negative photoresist composition as claimed in claim 1, herein said
photosensitizer comprises at least one polyhalogen compound selected from
the group consisting of compounds represented by the following general
formula (V):
Ar--CH.sub.3-p X.sup.2.sub.p).sub.q (V)
wherein p is an integer of 1 to 3; q is an integer of 1 or more; x.sup.2
stands for chlorine, bromine, or iodine; and Ar stands for a phenyl group,
a naphthyl group, a benzen sulfonyl group, an aminopyridine residue, an
s-triazine residue, a furan residue, or a thiophene residue.
7. A negative photoresist composition as claimed in claim 1, wherein the
content of said polyhalogen compound(s) as said photosensitizer based on
the total amount of said polyhalogen compound(s) and said
polyhydroxystyrene as said base resin is in the range of 1 mol % to 50 mol
%.
8. A negative photoresist composition as claimed in claim 1, wherein said
solvent is at least one compound selected from the group consisting of an
ester of acetic acid, ethers, lactones, and amides.
Description
Background of the Invention
1. Field of the Invention
The present invention relates to a negative photoresist composition for use
in the production of, for example, semiconductor devices.
2. Prior Art
Photoresist compositions (hereinafter often referred to simply as "resist")
are basic materials for use in the photolithography step in the production
of various semiconductor devices and the like.
As such resists, use has heretofore been made of, for example, cyclized
rubber type compositions comprising an isoprene rubber as the base resin
and a bisazide compound as the photosensitizer. As a dry etching technique
capable of microprocessing in the order of at most 3 .mu.m was developed
in step with the ever-increasing scale of integration of semiconductor
devices, however, an absolute necessity arose for a resist not only
capable of forming fine resist patterns but also resistant to a reactive
gas plasma generated during dry etching.
Positive acting novolak resists represented by, for example, "OFPR 800"
(trade name of a product manufactured by Tokyo Ohka K.K.) are known as
resists satisfying the above-mentioned requirements of fine resist pattern
formation and dry etching resistance. Such positive resists comprise a
cresol-formaldehyde resin [see the structural formula (1)] soluble in
alkali developers as the base resin and a 2-diazonaphthoqinonesulfonic
acid ester of polyhydroxybenzophenone [see the structural formulae (2) and
(3l)] as the photosensitizer.
##STR2##
[wherein in the structural formula (1), r is a positive integer.]
##STR3##
[wherein in the structural formulae (2) and (3), -DNQ stands for the
following structural formula (a) or (b).]
##STR4##
In the case of these positive novolak resists, the mechanism of resist
pattern formation is as follows.
In a positive resist prior to irradiation thereof with light, the
photosensitizer [of the structural formula (2) or (3)] hardly soluble in
an alkali developer dose not react with the base resin [of the structural
formula (1)]soluble in the developer.
A reduction type projection exposure apparatus, wherein the g line (436 nm
in wavelength) or the i line (365 nm in wavelength) from a mercury lamp is
utilized, is generally used for exposure of such a positive resist to
light. The above-mentioned photosensitizer, when irradiated with light
through the above-mentioned exposure to light, is converted into a
derivative of indenecarboxylic acid having polar carboxylic acid groups.
Since this derivative of indenecarboxylic acid is so soluble in the alkali
developer as to promote the dissolution of the light-irradiated
(light-exposed) areas of the novolak resin, a positive resist pattern can
be formed. In other words, pattern formation with this type of photoresist
compositions is effected through an interaction of the photosensitizer
capable of polarization upon exposure to light with the polar base resin.
The major reason for the use of the above-mentioned positive resist include
the following.
(i) The use of the alkali developer substantially obviates swelling of the
resist pattern while providing a resolution of about 1 to 2 .mu.m.
(ii) The effect of stabilizing the resist against ion energy in the form of
a reactive gas plasma or the like from the outside by resonance of many
aromatic rings, such as skeletal benzene rings, included in the resist as
shown in the structural formulae (1), (2) and (3) is great enough to
provide excellent dry etching resistance characteristics as compared with
the aforementioned cyclized rubber type resists.
(iii) The photosensitizer represented by the structural formula (2l) or (3)
are excellent in sensitivity within the range of exposure light
wavelengths.
As the demand for a higher scale of integration of semiconductor devices
has recently become increasingly strict, however, the fact is that a
dimensional accuracy of the submicron order is required as to the fineness
of resist patterns. As is well known, in projection type optical systems
having the same number of apertures in an objective lens, the resolution
of a resist pattern depends on the wavelength of exposure light in such a
way that the shorter the wavelength, the higher the resolution is. In view
of this, shortening the wavelength of light from a light source used in
photorithographic techniques is under investigation.
A deep ultraviolet region ranging from 200 to 300 nm in wavelength of
exposure light is presently utilized. Known short wavelength light sources
include a xenon-mercury (Xe-Hg) lamp as already widely used and an excimer
laser involving excitation of a mixed gas such as krypton-fluorine (Kr-F),
which has recently been put into practical use.
In general, the aforementioned positive novolak resist supposed to be
expose to light of the g line or the i line exhibits a large absorption
within the deep ultraviolet region, assigned to aromatic ring moieties
[see, for example, the structural formulae (1) to (3) and the structural
formulae (a) and (b), and hardly undergoes decomposition of such aromatic
ring moieties even when irradiated with light within the above-mentioned
region. As a result, the amount of exposure to light is larger in the
upper layer portion (portion closer to a light source) of a resist coating
film than in the lower layer portion thereof. This results in formation of
a resist pattern with a trapezoidal cross section in the case of a
positive resist. On the other hand, in the case of a conventional common
negative resist which exhibits a large absorption in the wavelength region
of 200 to 300 nm, a resist pattern with a reverse trapezoidal cross
section is obtained. Thus, in either case, a good resist pattern can
hardly be formed.
As a technique of forming a good resist pattern is known, for example, a
technique as disclosed in Literature I: "SPIE, vol. 631, Advances in
Resist Technology and Processing III" (pp. 68 to 74, 1986).
In positive resists involved with this technique, a tert-butoxy-carbonyl
derivative of styrene-maleimide copolymer represented by the structural
formula (4):
##STR5##
[wherein s is a positive integer] is used as the base resin, while a
2-diazonaphtoquinone compound represented by the structural formula (5):
##STR6##
[wherein --DNQ stands for the aforementioned structural formula (a) or
(b)] or diphenyliodonium trifluoromethanesulfonate represented by the
structural formula (6):
##STR7##
is used as the photosensitizer.
The mechanism of formation of a resist pattern from a resist as disclosed
in Literature I is as follows.
The base resin of the structural formula (4) is difficulty soluble in an
alkali developer. When the above-mentioned resist is irradiated with deep
ultraviolet radiation, the photosensitizer of the structural formula (5)
or (6) is converted into an acidic substance. Through a catalytic
interaction of the above-mentioned acidic substance with the base resin of
the structural formula (4), the tert-butoxycarbonyl groups of the base
resin are eliminated to form an imide compound. Since the resulting imide
compound is soluble in the alkali developer, a positive resist pattern
with a high resolution of about 1 .mu.m can be obtained using that alkali
developer.
The resist disclosed in the aforementioned Literature I are high in
sensitivity since the foregoing reaction brought about by irradiation with
deep ultraviolet radiation progresses in catalytic mode. Furthermore, the
compound of the structural formula (4) as the base resin exhibits a
reduced absorption within the deep ultraviolet region by virtue of
maleimide units introduced thereinto as compared with the aforementioned
compound of the structural formula (1). Accordingly, a resist pattern with
a close-to-rectangular cross section can be obtained.
However, the conventional photoresist compositions comprising the compound
of the aforementioned structural formula (4) as the base resin and the
compound of the aforementioned structural formula (5) or (6) as the
photosensitizer inevitably involve a problem of being lowered in
resistance to etching with a reactive gas plasma as mentioned above
because of introduction of maleimide units into the base resin with being
lowered in the aromatic ring content as compared with novolak resists.
Furthermore, where a substrate or the like as a base material is processed
with a mask consisting of a resist pattern formed from a conventional
negative resist as mentioned above the pattern cannot be transferred in
the same dimensions as those of the mask to make microprocessing
difficult.
In view of the above-mentioned problem of the prior art, an object of the
present invention is to provide a deep ultraviolet sensitive photoresist
composition excellent in resistance to etching with a reactive gas plasma
and capable of forming a resist pattern with a close-to-rectangular cross
section.
SUMMARY OF THE INVENTION
In order to attain the above-mentioned object, the present invention
provides a photoresist composition comprising a base resin, a
photosensitizer sensitive to deep ultraviolet radiation, and a solvent,
wherein said base resin comprises a polyhydroxystyrene represented by the
following structural formula (I):
##STR8##
(wherein k is a positive integer), and said photosensitizer comprises a
polyhalogen compound(s).
In embodying the present invention, the weight-average molecular weight of
the base resin of the structural formula (I) is preferably in the range of
1,000 to 100,000, more preferably in the range of 5,000 to 50,000. Such
polyhydroxystyrene can be easily synthesized from a vinylphenol derivative
through cationic polymerization, anionic polymerization or radical
polymerization, as disclosed in Literature II: "Polymer", vol. 24, p. 995,
1983, published by Butterworth & Co. Ltd. Polyhydroxystyrene resins having
a weight-average molecular weight of up to about 100,000 are available.
Such polyhydroxystyrene resins have a glass transition point of about 170
.degree. C. and absorption coefficient of about 0.25 .mu.m.sup.-1 and are
alkali-soluble. The photoresist composition of the present invention forms
a negative resist pattern. More specifically, polyhydroxystyrene as the
base resin is reacted with halogen radicals generated by irradiating the
photosensitizer with deep ultraviolet radiation to form a negative resist
pattern, as will be described in detail later. This gives rise to a
necessity for incorporation of a large amount of the photosensitizer into
the composition to meet the stoichiometrical relationship between the base
resin and the photosensitizer in the case where the polyhydroxystyrene has
a small weight-average molecular weight. In order to enhance the
sensitivity of the resist, therefore, the weight-average molecular weight
of the base resin is preferably designed to be at least 1,000.
Polyhalogen compounds sensitive to at least one kind of radiation selected
from among deep ultraviolet rays, X-rays, and electron beams are
preferable as the photosensitizer to be contained in the photoresist
composition of the present invention. Particularly preferred are
polyhalogen compounds which generate halogen radicals when irradiated with
deep ultraviolet radiation falling within the wavelength range of 200 to
300 nm. Such polyhalogen compounds having the above-mentioned properties
include various types of compounds, main preferable examples of which
include the following compounds: (a) dichloroalkanes and trichloroalkanes
represented by the following general formula (II):
R.sup.1 --CH.sub.3-l Cl.sub.l (II)
(wherein R.sup.1 stands for an alkyl group; and l is 2 or 3, (b)
polybromoalkanes and polyidoalkanes represented by the following general
formula (III)
C.sub.m H.sub.2m+2-n X.sup.1.sub.n (III)
(wherein X.sup.1 stands for bromine or iodine, and m and n are integers,
provided that they satisfy the formula:
1.ltoreq.n.ltoreq.2m+2),
(c) .alpha.-haloester compounds, .alpha.-halocarboxylic acid compounds,
.alpha.-haloketone compounds, .alpha.-haloaldehyde compounds,
.alpha.-haloamide compounds, N-alkylhaloamide compounds, and
N,N-dialkylhaloamide compounds all represented by following general
formula (IV):
##STR9##
wherein X.sup.2 stands for chlorine, bromine, or iodine; p is an integer
of 1 to 3; and Y stands, for an alkoxyl group (--OR.sup.1) in the case of
the .alpha.-haloester compounds, for a hydroxyl group (--OH) in the case
of the .alpha.-halocarboxyl acids, for an alkyl or aryl group (--R.sup.2)
in the case of the .alpha.-haloketone compounds, for hydrogen in the case
of the .alpha.-haloaldehyde compounds, for an amino group (--NH.sub.2) in
the case of the .alpha.-haloamide compounds, for a primary amine residue
(--NHR.sup.1) in the case of the N-alkylhaloamide compounds, or for a
secondary amine residue (--N.sub.2 R.sup.1) in the case of
N,N-dialkylhaloamide compounds], (d) a range of compounds represented by
the following general formula (V):
Ar--CH.sub.3-p X.sup.2.sub.p).sub.q (V)
(wherein p is an integer of 1 to 3; q is an integer of 1 or more; x.sup.2
stands for chlorine, bromine, or iodine; and Ar stands for a phenyl group,
a naphthyl group, a benzenesulfonyl group, an aminopyridine residue, an
s-triazine residue, a furan residue, or a thiophene residue)
The polyhalogen compounds represented by one of the foregoing general
formulae (II) to (V) are of a structure having halogen atoms with which at
least two hydrogen atoms bonded to a carbon atom at the .alpha.-position
of each corresponding unsubstituted compound have been substituted.
The alkyl group R.sup.1 in the above-mentioned general formula (II) is
preferably a primary alkyl such as methyl, ethyl or n-propyl; a secondary
alkyl such as isopropyl, 2-butyl or 2-pentyl; or a tertiary alkyl such as
2-methyl-2-propyl or 2-ethyl-2-propyl.
The alkoxyl group Y in the .alpha.-haloester compounds of the general
formula (IV) is preferably methoxy, ethoxy, isopropoxy, tert-butoxy, or
phenoxy.
The alkyl group Y in the .alpha.-haloketone compounds of the general
formula (IV) is preferably methy, ethyl, isopropyl, or tert-butyl, while
the aryl group Y in the above-mentioned compounds is preferably phenyl,
naphthyl, diphenyl, 4-pyridyl, p-chlorophenyl, or p-bromophenyl.
The primary amine residue Y in the N-alkylhaloamide compounds of the
general formula (IV) is preferably methylamino, ethylamino or anilino.
The secondary amino residue Y in the N,N-dialkylhaloamide compounds of the
general formula (IV) is preferably dimethylamino, diethylamino, or
N-methylanilino.
As is well known, most of halogen compounds except for many fluoroalkyl
compounds and simple monochloroalkyl compounds are capable of generating
halogen radicals when irradiated with deep ultraviolet radiation. Here,
taking alkyl halides having one carbon atom as an example, spectroscopic
data will be mentioned. The maximum absorbance (.lambda..sub.max) lies at
173 nm for CH.sub.3 CL, at 204 nm for CH.sub.3 Br and at 258 nm for
CH.sub.3 I, demonstrating that a halogen atom having a larger atomic
weight shifts the site of .lambda..sub.max in UV absorption spectrum
toward a longer wavelength. Likewise, the .lambda..sub.max lies at 258 nm
for CH.sub.3 I, at 292 nm for CH.sub.2 I.sub.2 and at 349 nm for
CHI.sub.3, demonstrating that a larger number of halogen atoms with which
hydrogen atoms bonded to one carbon atom have been substituted shift the
site of .lambda..sub.max in UV absorption spectrum toward a longer
wavelength. Accordingly, in the case of substitution of one compound with
a halogen atom(s), it is natural to guess that the larger the number of
substituent halogen atoms and/or the larger the atomic weight of a
substituent halogen atom(s), the higher the formation efficiency of
halogen radicals should be. Further, the bond of a carbon atom to a
halogen atom is easy of activation to form a halogen radical in the case
where a carbonyl group or an aromatic substituent is present in a position
adjacent to the above-mentioned carbon atom.
As will be understandable from the above, a wide variety of polyhalogen
compounds, which are readily available, are utilizable in the present
invention. Among those polyhalogen compounds, a compound having such
suitable properties of being solid and/or low in self-decomposability at a
baking temperature during drying of a resist coating film as to be adapted
for use in a photoresist composition may be chosen according to the
designing of the photoresist composition.
In embodying the present invention, the photosensitizer content of the
photoresist composition of the present invention which content is based on
the total amount of the photosensitizer and the base resin and represented
by the following numerical formula:
##EQU1##
is preferably in the range of 1 mol % to 50 mol %, more preferably in the
range of 2 mol % to 20 mol %, provided that the molar amount of the base
resin is calculated based on monomer units and hence defined as a value
obtained by dividing the weight of polyhydroxystyrene by the molecular
weight of hydroxystyrene of 120 in the instant specification. The lower
limit, 1 mol %, of the above-defined content is a minimum amount necessary
for securing substantial sensitivity of the photoresist composition, while
the upper limit, 50 mol %, of the above-defined content is a maximum
amount allowable for securing sufficient adhesion of a resist to an object
to be etched.
Also in embodying the present invention, a solvent to be contained in the
photoresist composition is preferably at least one member selected from
the group consisting of esters of acetic acid, ethers, lactones, and
amides. Preferred esters of acetic acid include 2-methoxyetyl acetate and
2-ethoxyethyl acetate. Preferred ethers include dioxane and
tetrahydrofuran. Preferred lactones include
.alpha.-butyrolactone. Preferred amides include N,N-dimethylformamide and
N,N-dimethylacetamide.
The photoresist composition of the present invention comprises
polyhydroxystyrene represented by the aforementioned structural formula
(I) and a polyhalogen compound represented by any one of the
aforementioned general formulae (II) to (V). The mechanism of formation of
a resist pattern from the above-mentioned photoresist composition is
believed to be as follows.
The polyhalogen compound (generically represented by R-X) as the
photosensitizer generates halogen radicals (represented by X.sub..cndot.)
when irradiated with deep ultraviolet radiation.
R-X.fwdarw.R.sup..cndot. +X.sup..cndot.
The halogen radicals abstract hydrogen atoms from the benzyl positions of
the polyhydroxystyrene to form polymer radicals. Subsequently, the polymer
radicals crosslink therebetween to polymerize themselves. As a result, a
negative resist pattern which is hard to dissolve in a developer (an
organic solvent or an aqueous solution of an alkali) is obtained.
##STR10##
(wherein the formulae are drawn with a focus on hydroxystyrene units and
one halogen radical).
Since formation of resist pattern is achieved with such halogen radicals,
the photosensitizer content necessary for resist pattern formation can be
decreased with no substantial decrease in the aromatic ring content of the
whole photoresist composition. This is believed to contribute to an
improvement in etching resistance characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects and advantages of the present invention
will be better understood by reference to the following description taken
in connection with the accompanying drawings, in which:
FIGS. 1(a) and (b) are schematic cross-sectional views of an intermediate
structure and a structure with a resist pattern, respectively, produced in
the course of a process for forming a resist pattern on a substrate, which
are illustrative of examples of the photoresist composition of the present
invention;
FIG. 2 is a schematic illustration of the structure of an exposure
apparatus, which was used in Examples according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A detailed description will now be made of Examples according to the
present invention. While specific conditions will be exemplified in the
following Examples to facilitate the understanding of the present
invention, it is to be understood that the following Examples should not
be construed as limiting the scope of the present invention. Some of
chemicals mentioned in the following Examples are not accompanied by
mentioned of their origins. However, all of them used were chemically
sufficiently pure and are readily available.
SENSITIVITY IN RESIST PATTERN FORMATION AND RESOLUTION OF RESIST PATTERN
Some photoresist compositions according to the present invention will be
exemplified before a description of results of measurements of
sensitivities of the photoresist composition comprising one of various
polyhalogen compounds as the photosensitizer in actual resist pattern
formation therefrom as well as resolutions of the resulting resist
patterns.
EXAMPLES 1 TO 12
Resists 1 to 12 used in the measurements will first be described with
centering on their compositions comprising a base resin and a
photosensitizer with a photosensitizer content as defined hereinbefore.
In order to facilitate the comparison of the results of the measurements,
one polyhydroxystyrene resin having a weight-average molecular weight of
18,800 was used as the base resin in combination with various
photosensitizers to prepare various resists. The preparation of these
resists was done throughout at room temperature.
Resist 1
90 mmol (11 g) of polyhydroxystyrene having a weight-average molecular
weight of 18,800 was mixed with 10 mmol (1.62 g) of trichloroacetamide
(C1.sub.3 CCONH.sub.2) as one of polyhalogen compounds of the type
classified under the aforementioned general formula (IV). the resulting
mixture was dissolved in 50 ml of 2-methoxyethyl acetate as a solvent.
Thereafter, the resulting solution was filtrated through a porous membrane
filter of 0.2 .mu.m in pore size to obtain Resist 1. As will be
understandable from the foregoing description, the trichloroacetamide
content of the Resist 1 as defined hereinbefore was 10 mol %.
Resist 2
95 mmol of polyhydroxystyrene as mentioned before was mixed with 5 mmol
(2.16 g) of tris(tricloromethyl)-s-triazine, which is one of polyhalogen
compounds of the type classified under the aforementioned general formula
(V) and is represented by the following structural formula (6):
##STR11##
The resulting mixture was dissolved in 50 ml of 2-methoxyethyl acetate as a
solvent. Thereafter, the resulting solution was filtrated in the same
manner as in the preparation of the Resist 1 to obtain Resist 2. The
photosensitizer content of the Resist 2 was 5 mol %.
Resist 3
90 mmol of polyhydroxystyrene as mentioned before was mixed with 10 mmol
(2.65 g) of 2,4-dichlorobenzotrichloride, which is one of polyhalogen
compounds of the type classified under the aforementioned general formula
(V) and is represented by the following structural formula (7):
##STR12##
The resulting mixture was dissolved in 50 ml of 2-methoxyethyl acetate as
a solvent. Thereafter, the resulting solution was filtrated in the same
manner as in the preparation of the Resist 1 to obtain Resist 3. The
photosensitizer content of the Resist 3 was 10 mol %.
Resist 4
90 mmol of polyhydroxystyrene as mentioned before was mixed with 10 mmol of
dichloroacetamide (Cl.sub.2 CHCONH.sub.2) as one of the polyhalogen
compounds of the type classified under the aforementioned general formula
(IV). The resulting mixture was dissolved in 50 ml of 2-methoxyethyl
acetate as a solvent. Thereafter, the resulting solution was filtrated in
the same manner as in the preparation of the Resist 1 to obtain Resist 4.
The photosensitizer content of the Resist 4 was 10 mol %.
Resist 5
90 mmol of polyhydroxystyrene as mentioned before was mixed with 10 mmol of
tribromoquinaldine, which is one of polyhalogen compounds of the type
classified under the aforementioned general formula (V) and is represented
by the following structural formula (8);
##STR13##
The resulting mixture was dissolved in 50 ml of 2-methoxyethyl acetate as
a solvent. Thereafter, the resulting solution was filtrated in the same
manner as in the preparation of the Resist 1 to obtain Resist 5. The
photosensitizer content of the Resist 5 was 10 mol %.
Resist 6
Resist 6 was prepared using substantially the same procedure as in the
preparation of the Resist 3 except that 2,4-dichlorobenzotrichloride as
mentioned before [structural formula (7)] was used in such an amount as to
provide a photosensitizer content of 5 mol %.
Resist 7
Resist 7 was prepared using substantially the same procedure as in the
preparation of the Resist 2 except that tris(tricloromethyl)-s-triazine as
mentioned before [structural formula (6)] was used in such an amount as to
provide a photosensitizer content of 10 mol %.
Resist 8
90 mmol of polyhydroxystyrene as mentioned before was mixed with 10 mmol of
tribromomethyl phenyl sulfone, which is one of polyhalogen compounds of
the type classified under the aforementioned general formula (V) and is
represented by the following structural formula (9);
##STR14##
The resulting mixture was dissolved in 50 ml of 2-methoxyethyl acetate as
a solvent. Thereafter, the resulting solution was filtrated in the same
manner as in the preparation of the Resist 1 to obtain Resist 8. The
photosensitizer content of the Resist 8 was 10 mol %.
Resist 9
Resist 9 was prepared using substantially the same procedure as in the
preparation of the Resist 8 except that tribromomethyl phenyl sulfone as
mentioned before [structural formula (9)] was used in such an amount as to
provide a photosensitizer content of 5 mol %.
Resist 10
90 mmol of polyhydroxystyrene as mentioned before was mixed with 10 mmol of
carbon tetrabromide (CBR.sub.4) as one of the polyhalogen compounds of the
type represented by the aforementioned general formula (III) in the
presence of 10 mmol of dimethylaminopyridine. The resulting mixture was
dissolved in 50 ml of 2-methoxyethyl acetate as a solvent. Thereafter, the
resulting solution was filtrated in the same manner as in the preparation
of the Resist 1 to obtain Resist 10. The photosensitizer content of the
Resist 10 was 10 mol %. The dimethylaminopyridine contained in the Resist
10 serves to promote the generation of halogen radicals from carbon
tetrabromide as is well known.
Resist 11
90 mmol of polyhydroxystyrene as mentioned before was mixed with 10 mmol of
p-bromophenancyl bromide, which is one of polyhalogen compounds of the
type classified under the aforementioned general formula (IV) and is
represented by the following structural formula (10);
##STR15##
The resulting mixture was dissolved in 50 ml of 2-methoxyethyl acetate as
a solvent. Thereafter, the resulting solution was filtrated in the same
manner as in the preparation of the Resist 1 to obtain Resist 11. The
photosensitizer content of the Resist 11 was 10 mol %.
Resist 12
Resist 12 was prepared using substantially the same procedure as in the
preparation of the Resist 4 except that a mixed solvent composed of
2-methoxyethyl acetate and isoamyl acetate at a weight ratio of 1:9 was
used instead of 2-methoxyethyl acetate alone. The photosensitizer
(dichloroacetamide) content of the Resist 12 was 10 mol %.
The procedure of forming a resist pattern using each of the foregoing
Resists 1 to 12 will be described while referring to FIGS. 1(a) and (b).
FIGS. 1(a) and 1(b) are schematic cross-sectional illustrations of an
intermediate structure and a structure with a resist pattern produced in
the course of a process for forming a resist pattern, by reference to
which illustrations a description will be made of the procedure of the
measurements of sensitivity and resolution in the following Examples. In
the figures, hatching indicative of cross section was partially omitted.
As shown in FIG. 1(a), a reflection preventive layer 13 of 1 .mu.m in
thickness from which photosensitivity was eliminated through thermal cure
was formed on the upper surface of a silicon substrate 11 as an object to
be etched. Additionally stated, the reflection preventive layer was
provided for accommodation to comparison in sensitivity, and hence is
different from such a reflection preventive layer as used in a
photolithographic process for producing a device. Any material can be used
to form the above-mentioned reflection preventive layer in so far as it
can completely absorb light which was passed through a resist.
In the Examples, a photoresist "MP 2400" (trade name of a product
manufactured by Shipley) was used as the material of the reflection
preventive layer 13 since it is easy of thermal cure.
Subsequently, each of the solutions of the Resists 1 to 12 was applied on
the surface of the above-mentioned reflection preventive layer 13 by spin
coating, soft-baked using a hot plate at a temperature of 100 .degree. C.
for 1 minute to form a resist layer 15 of 1 .mu.m in thickness. Thus, a
structure 17 to be exposed to deep ultraviolet radiation was obtained.
The above-mentioned reflection preventive layer 13 was supposed to prevent
deep ultraviolet radiation once transmitted through the resist layer 15
upon irradiation therewith of the structure 17 from being reflected to
enter the resist layer 15.
The structure 17 of FIG. 1(a) thus obtained was irradiated with deep
ultraviolet radiation emitted from a Xe-Hg lamp (an aligner PLA 501
equipped with a cold mirror CM 250, manufacture by Canon Inc.,
wavelengths: 220 to 300 nm) while using a quartz mask in close contact
with the resist layer 15.
Thereafter, the irradiated structure 17 was subjected to development with
an alkali developer "MF 312" (trade name of product manufactured by
Shipley), diluted four-fold by volume with pure water and maintained at a
temperature of 23.degree. C., for a predetermined period of time, and was
then rinsed with pure water for 30 seconds to obtain a measurement sample
19 having a negative resist pattern as shown in FIG. 1(b).
Subsequently, the cross-section of the sample thus obtained was observed
with an electron microscope to measure the dimension d.sub.1 of the
uppermost portion of the pattern and the dimension d.sub.2 of the
minimum-sized portion of the pattern as shown in FIG. 1(b), from which the
amount of overhang as defined by a formula: (d.sub.1 -d.sub.2)/2 was
calculated.
In a repetition of the foregoing resist pattern formation, the resolvable
dimension of pattern just before the dimension d.sub.2 gets a value of
substantial zero is referred to as "minimum resolvable dimension".
Attached Table 1 shows the results of measurements of sensitivity in terms
of minimum dosage of deep ultraviolet radiation necessary for securing a
given rate of a residual film remaining after development as well as
minimum resolvable dimension and amount of overhang with respect to the
aforementioned Resists 1 to 12 under Examples 1 to 12, respectively.
As can be understood from attached Table 1, the Resists 1, 2, 4, 7 and 12
used in Examples 1, 2, 4, 7 and 12 used in Examples 1, 2, 4, 7 and 12
provided an amount of overhang of 0 .mu.m with a rectangular cross section
of a resist pattern even when the minimum disolvable dimension was 0.5
.mu.m. The Resists 3, 6 and 9 to 11 used in Examples 3, 6, and 9 to 11
provided a minimum resolvable dimension of 0.5 .mu.m and an amount of
overhang of 0.1 .mu.m (in Example 9) or smaller to form a resist pattern
with a high resolution. It also can be understood that the Resists 5 and 8
used in Examples 5 and 8 provided a minimum resolvable dimension of 1.0
.mu.m and of 0.2 .mu.m or smaller.
It can further understood from the results as dosage that the resists
wherein the photosensitizer used was tris(trichloromethyl)-s-triazine
(Examples 2 and 7), 2,4-dichlorobenzotrichloride (Examples 3 and 6),
tribromomethyl phenyl sulfone (Examples 8 and 9), carbon tetrabromide in
the presence of dimethylaminopyridine (Example 10), or p-bromophenancyl
bromide (Example 11) exhibited a comparatively excellent sensitivity.
EXAMPLES 13 to 18
In the following Examples, two series of resists differing in the
weight-average molecular weight of polyhydroxystyrene used therein were
prepared, and resist patterns were formed from the resists to give results
of the measurements, which will be described later while referring to
Attached Table 2.
A description will first be made of Resists 13 to 18 used in the
measurements in Examples 13 to 18.
Resist 13
Resist 13 was prepared using 5 mmol of tris(trichloromethyl)-s-triazine as
the photosensitizer and 50 ml of 2-methoxyethyl acetate as the solvent in
substantially the same manner as in the preparation of the Resist 2 except
that 95 mmol of polyhydroxystyrene having a weight-average molecular
weight of 48,800 was used.
Resist 14
Resist 14 was prepared using 5 mmol of tris(trichloromethyl)-s-triazine as
the photosensitizer and 50 ml of 2-methoxyethyl acetate as the solvent in
substantially the same manner as in the preparation of the Resist 2 except
that 95 mmol of polyhydroxystyrene having a weight-average molecular
weight of 5,000 was used.
Resist 15
Resist 15 was prepared using 5 mmol of tris(trichloromethyl)-s-triazine as
the photosensitizer and 50 ml of 2-methoxyethyl acetate as the solvent in
substantially the same manner as in the preparation of the Resist 2 except
that 95 mmol of polyhydroxystyrene having a weight-average molecular
weight of 1,600 was used.
Resist 16
Resist 16 was prepared using 10 mmol of 2,4-dichlorobenzotrichloride as the
photosensitizer and 50 ml of 2-methoxyethyl acetate as the solvent in
substantially the same manner as in the preparation of the Resist 3 except
that 90 mmol of polyhydroxystyrene having a weight-average molecular
weight of 48,800 was used.
Resist 17
Resist 17 was prepared using 10 mmol of 2,4-dichlorobenzotrichloride as the
photosensitizer and 50 ml of 2-methoxyethyl acetate as the solvent in
substantially the same manner as in the preparation of the Resist 3 except
that 90 mmol of polyhydroxystyrene having a weight-average molecular
weight of 5,000 was used.
Resist 18
Resist 18 was prepared using 10 mmol of 2,4-dichlorobenzotrichloride as the
photosensitizer and 50 ml of 2-methoxyethyl acetate as the solvent in
substantially the same manner as in the preparation of the Resist 3 except
that 90 mmol of polyhydroxystyrene having a weight-average molecular
weight of 1,600 was used.
The Resists 13 to 18 were each used to form a resist pattern according to
the same procedure as in Examples 1 to 12 already described while
referring to FIGS. 1(a) and (b).
As will be understandable from Attached Table 2, there is tendency that a
larger dosage of deep ultraviolet radiation is required as the
weight-average molecular weight of polyhydroxystyrene used as the base
resin in combination with the same photosensitizer is smaller. This is
believed to be affected by the absorption coefficient of
polyhydroxystyrene as mentioned in Table 1.
TABLE 1
______________________________________
Weight-Average Molecular Weight
Absorption Coefficient
of Polyhydroxystyrene
(.mu.m .sup.-1)
______________________________________
48,800 0.29
18,800 0.70
5,000 0.52
1,600 0.79
______________________________________
EXAMPLES 19 to 26
A description will now be made of Examples wherein a krF excimer laser was
used as a light source in place of the Xe-Hg lamp in the course of resist
pattern formation.
The excimer laser used in these Examples was of an optical system as
illustrated in FIG. 2.
As shown in FIG. 2, deep ultraviolet radiation (wavelength: about 250 nm)
emitted from laser oscillator 21 (manufactured by Lambda Physics) is
guided to lens system 25 by means of a reflective mirror 23. A structure
17 [see FIG.1(a)] in close contact with a mask 27 is irradiated with a
laser beam which has passed through the lens system 25. In the Examples,
the structure 17 with the same thickness of layers as in Examples 1 to 18
was irradiated with a laser beam pulse energy of 4.1 mJ/cm.sup.2 and
subjected to development under the same conditions as in Examples 13 to
18.
Resists used in the Examples and results of measurements obtained therein
will be described while referring to Attached Table 3.
In Examples 19 to 22, tris(trichloromethyl)-s-triazine was used as a
photosensitizer to prepare resists differing only in the weight-average
molecular weight of polyhydroxystyrene. More specifically, the resist used
in Example 19 corresponds to the aforementioned Resist 13, the resist used
in Example 20 to the aforementioned Resist 2, and the resists used in
Examples 21 and 22 to the aforementioned Resists 14 and 15, respectively.
As will be understandable from the resist of measurements in Examples 19 to
22, a minimum resolvable dimension of at most 0.5 .mu.m can be attained by
irradiation using the excimer laser, and there is a tendency that a larger
dosage is required as the weight-average molecular weight of
polyhydroxystyrene is smaller, just as described in Examples 13 to 15.
In Examples 23 to 26, 2,4-dichlorobenzotrichloride was used as a
photosensitizer to prepare resists differing only in the weight-average
molecular weight of polyhydroxystyrene, which were used to form resist
patterns with results of measurements as shown in Attached Table 3. The
resist used in Example 23 corresponds to the aforementioned Resist 16, the
resist used in Example 24 to the aforementioned Resist 3, and the resists
used in Examples 25 and 26 to the aforementioned Resists 17 and 18,
respectively.
As will be understandable from the results of measurements in Examples 23
to 26 as well, a minimum resolvable dimension of at most 0.5 .mu.m can be
attained by irradiation using the excimer laser, and there is a tendency
that a larger dosage is required as the weight-average molecular weight of
polyhydroxystyrene is smaller.
COMPARISON EXAMPLE 1
The same reflection preventive layer as formed in the foregoing Examples
was formed on the same substrate as used in the foregoing Examples.
Thereafter, a negative resist layer was formed on the reflection
preventive layer. As the negative resist, use was made of "Laycast
RD-2000N" (trade name of a negative resist containing a bisazide as the
photosensitizer and polyhydroxystyrere, manufactured by Hitachi Chemical
Co., Ltd.). The above-mentioned negative resist layer having a thickness
of 1 .mu.m was formed by applying the above-mentioned negative resist on
the above-mentioned reflection preventive layer according to spin coating
at 5,000 r.p.m. and baking the resulting resist coating film using a hot
plate at a temperature of 80.degree. C. for 1 minute. The resulting
structure in close contact with a mask was irradiated with deep
ultraviolet radiation emitted from a Xe-Hg lamp (equipped with a cold
mirror CM 250) for 2 seconds, subjected to development with a developer RD
(trade name of product manufactured by Hitachi Chemical Co.,Ltd.) for 90
seconds, and rinsed with pure water for 60 seconds. The resulting
structure was post-baked using a hot plate at a temperature of 140
.degree. C. for 1 minute to obtain a resist pattern.
The cross section of the obtained resist pattern was observed to find out
that the amount of overhang in the pattern of 1 .mu.m lines and spaces was
0.4 .mu.m. This result is listed under Comparison Example 1 in Attached
Table 4.
The foregoing description has been made of Resists 1 to 26 exemplified as
photoresist compositions according to the present invention and the
resolutions of the resist patterns formed therefrom in Examples 1 to 26.
Conventional deep ultraviolet sensitive positive photoresist compositions
are hard to compare with the negative Resists 1 to 26 used in the
foregoing Examples. According to the aforementioned Literature I, however,
it is believed that the resists according to the present invention are
comparable in sensitivity inferred from dosage to the conventional
positive photoresist compositions, and are higher in resolution in terms
of minimum resolvable dimension than the conventional positive photoresist
compositions.
As is apparent from a comparison of Examples with Comparison Example 1, the
negative photoresist composition of the present invention is higher in not
only sensitivity but also resolution than the conventional negative
photoresist composition in view of the fact that the amounts of overhang
in the Examples were at most about 1/10 of that in Comparison Example 1.
EXAMPLES 27 to 28
A description will now be made of dry etching resistance characteristics as
measured using a sample prepared by applying a resist on the surface of a
silicon substrate, drying the resulting resist coating film to form a
resist layer of 1 .mu.m in thickness and developing the resist layer to
form a resist pattern of 1 .mu.m lines and spaces.
EXAMPLE 27
In Example 27, a sample as mentioned above was prepared using the
aforementioned Resist 3, and subjected to a dry etching treatment effected
in a mixed gas of oxygen-carbon tetrafluoride (containing 10 vol. % of
oxygen) with a parallel plate type dry etching apparatus "DEM 451"
(manufactured by ANELVA Corporation) to examine the dry etching resistance
characteristics of resist pattern of 1 .mu.m lines and spaces. The
pressure of the mixed gas was 2 Pa and the gas flow rate was 50 sccm,
while power density was 0.12W/cm.sup.2.
The thickness of the resist pattern of the sample was measured with "Tally
Step" (trade name of a product manufactured by Tailor Hobson) before and
after the dry etching treatment. The etching rate was calculated from the
amount of a decrease in the thickness of the resist pattern for an etching
time of 10 minutes. As a result, it was found that the resist pattern
formed in Example 27 was etched at a rate of 7.9 nm/min, while the amount
of dimensional decrease in the width of the lines of the resist pattern
was 50 nm. These results are listed in Attached Table 5.
EXAMPLE 28
In Example 28, the same sample as in Example 27 was prepared and subjected
to a dry etching treatment with the same apparatus as used in Example 27
using effected with the same apparatus as used in Example 27 using carbon
tetrachloride gas instead of the mixed gas of oxygen-carbon tetrafluoride
used in Example 27. The gas pressure was 10 Pa and the gas flow rate was
20 sccm, while the power density was 0.16W/cm.sup.2.
As a result, it was found out that the resist pattern was etched at a rate
of 11.0 nm/min in Example 28.
COMPARISON EXAMPLES 2 AND 3
For comparison, samples of Comparison Examples 2 and 3 were prepared using
as resists a tert-butoxycarbonyl derivative of styrene-maleimide copolymer
(1:1 copolymer, weight-average molecular weight: 6,500) as disclosed in
the aforementioned Literature I and the aforementioned "OFPR 800",
respectively. Each sample was subjected to a dry etching treatment under
the same conditions as in Example 27 to examine the dry etching resistance
characteristics of a resist pattern of 1 .mu.m lines and spaces. The
etching rate and the amount of a dimensional decrease in the width of
lines of the resist pattern were measured in the same manner as in Example
27.
As a result, it was found that the resist patterns of the samples of
Comparison Examples 2 and 3 were etched at rates of 10.1 nm/min and 7.7
nm/min, respectively, as compared with the etching rate of 7.9 nm/min in
Example 27 as already mentioned, while the amount of a dimensional
decrease in the width of the lines was 300 nm in Comparison Example 2 and
200 nm in Comparison Example 3. These results are also listed in Attached
Table 5.
As can be seen from the foregoing results, the resist pattern of the sample
of Example 27 which was formed from the photoresist composition comprising
polyhydroxystyrene according to the present invention is superior in
etching resistance characteristics to the resist pattern formed from the
conventional deep ultraviolet sensitive resist (Comparison Example 2), and
substantially comparable in etching resistance characteristics to the
resist pattern formed from the novolak resist (comparison Example 3).
Contrary to Example 28, the resist patterns of the same samples as in
Comparison Examples 2 and 3 were etched at rates of 16.0 nm/min and 10.0
nm/min, respectively.
As can be understood from the foregoing results, even in the case of a dry
etching system using carbon tetrachloride, the resist pattern of the same
sample of Example 27 which was formed from the photoresist composition
according to the present invention is superior in etching resistance
characteristics to the resist pattern formed from the conventional deep
ultraviolet sensitive resist (Comparison Example 2), and substantially
comparable in etching resistance characteristics to the resist pattern
formed from the novolak resist (Comparison Example 3).
As described heretofore with exemplification of Examples 1 to 28, the
photoresist composition of the present invention has a resolution
comparable or superior to conventional deep ultraviolet sensitive
photoresist compositions as well as etching resistance characteristics
comparable to conventional novolak photoresist compositions.
While the present invention has been described with reference to the
Examples, it will be obvious to those skilled in the art that the present
invention is not ineffective unless it is restricted to the foregoing
Examples.
For example, the resolution of the photoresist composition of the present
invention can be improved by using therein polyhydroxystyrene reduced by
means of catalytic reduction or hydride to decrease deep ultraviolet
absorption thereof because the phenolic hydroxyl groups [see the
structural formula (1)] of polyhydroxystyrene, which is readily available
on the market, are generally easy of oxidation to occasionally make the
photoresist composition liable to greatly absorb deep ultraviolet
radiation.
When the photoresist composition of the present invention is to be stored
in a state of being dissolved in a solvent, the use of an acetate solvent
as used in the foregoing Examples, an ether solvent such as dioxane or
tetrahydrofuran, a lactone solvent such as .gamma.-butyrolactone, or an
amide solvent such as N,N-dimethylformamide, N-methylpyrrolidone or
hexamethylphosphoric triamide can keep the base resin and/or the
photosensitizer from precipitating and permits the photoresist composition
to be applied in uniform thickness.
While the specific polyhalogen compounds have been exemplified in the
foregoing Examples, photosensitizers usable in the present invention are
not limited to only those exemplified substances. Any photosensitizer can
provide the same effects as in the foregoing Examples in so far as it can
generate halogen radicals when irradiated with deep ultraviolet radiation.
While the foregoing description is concerned with a case where the
photoresist composition of the present invention is irradiated with deep
ultraviolet radiation, electron beams or X-ray may be used in place of
deep ultraviolet radiation. Since a polyhalogen compound undergoes
photolysis when irradiated with deep ultraviolet radiation, it is natural
to guess that the polyhalogen compound should undergo sufficient
photolysis when irradiated with accelerated electron beams, X-rays or
other radiation, which is higher in energy than deep ultraviolet
radiation. Accordingly, the photoresist composition of the present
invention is also usable as an electron beam sensitive resist and an X-ray
sensitive resist.
It will be obvious to those skilled in the art that the foregoing materials
and numerical and other conditions are capable of arbitrary and suitable
alternation and modification in design within the purview of the object of
the present invention.
As is apparent from the foregoing Examples, the photoresist composition of
the present invention comprising at least a combination of
polyhydroxystyrene as the base resin with a polyhalogen compound as the
photosensitizer is not lowered in the content of aromatic rings attributed
to the base resin, unlike a photoresist composition comprising a base
resin having maleimide units introduced thereinto. Therefore, the
photoresist composition of the present invention is not spoiled in etching
resistance characteristics and can form a resist pattern with a high
resolution through the pattern formation mechanism wherein halogen
radicals are utilized.
Thus, photoresist composition of the present invention has dry etching
resistance characteristics comparable to those of conventional positive
novolak photoresist compositions and can form a resist pattern with
vertical sidewall profiles. Accordingly, processing of a base material
with such a resist pattern as the mask can accurately transfer the pattern
of the mask to the base material. This makes microprocessing possible.
Attached TABLE 1
__________________________________________________________________________
Minimum
Resolvable
Amount of
Kind of Photosensitizer
Development*.sup.1
Dosage
Dimension
Overhang
Photosensitizer content (mol %)
Time (sec)
(mJ/cm.sup.2)
(.mu.m)
(.mu.m)
__________________________________________________________________________
Ex. 1
trichloroacetamide
10 80 350 0.5 0
Ex. 2
tris(trichloromethyl)-
5 60 100 0.5 0
s-triazine
Ex. 3
2,4-dichlorobenzo-
10 110 200 0.5 0.05
trichloride
Ex. 4
dichloroacetamide
10 80 400 0.5 0
Ex. 5
tribromoquinaldine
10 160 600 1.0 0.2
Ex. 6
2,4-dichlorobenzo-
5 110 140 0.5 0.02
trichloride
Ex. 7
tris(trichloromethyl)-
10 70 100 0.5 0
s-triazine
Ex. 8
tribromomethyl phenyl
10 170 200 1.0 0.15
sulfone
Ex. 9
tribromomethyl phenyl
5 170 160 0.5 0.1
sulfone
Ex. 10
carbon tetrabromide
10 150 100 0.5 0.05
(in the presence of
dimethylaminopyridine)
Ex. 11
p-bromophenancyl bromide
10 120 100 0.5 0.02
Ex. 12
dichloroacetamide
10 50 400 0.5 0
__________________________________________________________________________
*.sup.1 A 1:3 mixture of "MF 312" and water was used as the developer.
Attached TABLE 2
__________________________________________________________________________
Weight-Average
Molecular Photo- Minimum
Weight of Kind of sensitizer Resolvable
Amount of
Polyhydroxy- Photo- Content
Development
Dosage
Dimension
Overhang
styrene sensitizer
(mol %)
Time (sec)
(mJ/cm.sup.2)
(.mu.m)
(.mu.m)
__________________________________________________________________________
Ex. 13
48,800 tris(trichloro-
5 90*.sup.1
50 0.5 0
methyl)-s-
triazine
Ex. 14
5,000 tris(trichloro-
5 30*.sup.1
250 0.4 0
methyl)-s-
triazine
Ex. 15
1,600 tris(trichloro-
5 30*.sup.2
600 0.35 0
methyl)-s-
triazine
Ex. 16
48,800 2,4-dichlorobenzo-
10 130*.sup.1
100 0.5 0.05
trichloride
Ex. 17
5,000 2,4-dichlorobenzo-
10 80*.sup.1
350 0.5 0
trichloride
Ex. 18
1,600 2,4-dichlorobenzo-
10 30*.sup.2
700 0.4 0
trichloride
__________________________________________________________________________
*.sup.1 A 1:3 mixture of "MF 312" and water was used as the developer.
*.sup.2 A 1:4 mixture of "MF 312" and water was used as the developer.
Attached TABLE 3
__________________________________________________________________________
Weight-Average
Molecular Photo- Minimum
Weight of Kind of sensitizer Resolvable
Amount of
Polyhydroxy- Photo- Content
Development
Dosage
Dimension
Overhang
styrene sensitizer
(mol %)
Time (sec)
(mJ/cm.sup.2)
(.mu.m)
(.mu.m)
__________________________________________________________________________
Ex. 19
48,800 tris(trichloro-
5 90*.sup.1
349 0.5 0
methyl)-s-
triazine
Ex. 20
18,800 tris(trichloro-
5 70*.sup.1
246 0.4 0
methyl)-s-
triazine
Ex. 21
5,000 tris(trichloro-
5 30*.sup.1
898 0.4 0
methyl)-s-
triazine
Ex. 22
1,600 tris(trichloro-
5 30*.sup.2
1098 0.4 0
methyl)-s-
triazine
Ex. 23
48,800 2,4-dichlorobenzo-
10 130*.sup.1
107 0.5 0.02
trichloride
Ex. 24
18,800 2,5-dichlorobenzo-
10 110*.sup.1
176 0.4 0
trichloride
Ex. 25
5,000 2,4-dichlorobenzo-
10 80*.sup.1
690 0.35 0
trichloride
Ex. 26
1,600 2,4-dichlorobenzo-
10 30*.sup.2
1025 0.35 0
trichloride
__________________________________________________________________________
*.sup. 1 A 1:3 mixture of "MF 312" and water was used as the developer.
*.sup.2 A 1:4 mixture of "MF 312" and water was used as the developer.
Attached TABLE 4
__________________________________________________________________________
Amount of
Dosage Development
Overhang
Kind of Resist
Light Source
(mJ/cm.sup.2)
Developer
Time (sec)
(.mu.m)
__________________________________________________________________________
Comp. Ex. 1
negative resist
Xe--Hg lamp
80 developer RD
90 0.4
(Laycast RD-2000N)
__________________________________________________________________________
Attached TABLE 5
__________________________________________________________________________
Etching Rate
Dimensional Decrease in Width
Kind of Resist
(nm/min)
of Line of Resist Pattern (nm)
__________________________________________________________________________
Ex. 27 Resist 3 as used
7.9 50
in Ex. 3
Comp. Ex. 2
resist as mentioned
10.1 300
in Literature I
Comp. Ex. 3
OFPR 800 (manufactured
7.7 200
by Tokyo Ohka K.K.)
__________________________________________________________________________
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